This invention relates generally to integrating accelerometers and, more particularly, to an integrating accelerometer assembly requiring more than a single acceleration-time pulse before actuation occurs.
Integrating accelerometers, acceleration switches, and inertial devices are widely used to measure forces resulting from changes in velocity, and to actuate a switch or the like in response to sensing a predetermined acceleration pulse. Such devices include some type of sensing mass, such as a piston, suspended so as to be affected by acceleration forces; i.e. the piston moves and thereby serves to open or close an electrical switch or switches.
The device may be filled with a fluid for damping motion, or contain a mechanical escapement or other delay mechanism so as to prevent premature or accidental actuation of the switch. Thus, the prior art accelerometer has the capability of protecting against actuation in response to a false signal, such as a short duration, high g-force, vibration or shock. This arrangement protects against such inadvertent actions as dropping, or simply an accidental crash during transportation.
One possible use of such an accelerometer is in a rocket arming circuit. For obvious reasons of safety, it is desirable that such circuits of the rocket payload not be actuated until the rocket has experienced a normal launch environment. For example, the prior art devices have been successfully used in protecting single stage rocket systems from being prematurely armed. For additional safety, it is also desirable not to arm a rocket payload when the rocket, normally launched by multiple launch boosters or stages, experiences activation of only one of the launch stages, as might occur in an accidental launch. Present integrating accelerometers, such as shown in U.S. Pat. No. 3,919,941 to Breed et al and U.S. Pat. No. 4,345,124 to Abbin Jr. et al, clearly do not have this capability as pointed out above. These prior art devices when used in a multiple stage rocket would simply actuate if the magnitude of acceleration-time pulse of the first stage is of proper value and for sufficient length of time regardless of the proper ignition and operation of the following stages and generation of subsequent acceleration-time pulses.
Thus, a need is identified for an integrating accelerometer assembly that responds to multiple acceleration pulses applied in series. Such an accelerometer would provide greatly improved safety as, for example, in the event of inadvertent launch due to firing of any single stage of a multi-stage rocket.